M3_DP

• Fertilization


  The process by which sperm and ovum - the male and female gametes, or sex cells - combine to create a single cell called a zygote
• Zygote


  The single cell created when sperm and ovum combine, which then duplicates itself again and again by cell division to produce all the cells that make up a baby
• Dizygotic (fraternal) twins


  • Result of two separate eggs being fertilized by two different sperm to form two unique individuals
  • Tend to run in families
  • Result of multiple eggs being released at one time
  • May have a genetic basis
• Monozygotic (identical) twins


  • Result of the cleaving of one fertilized egg
  • Generally genetically identical
• Heredity


  The genetic transmission of heritable characteristics from parents to offspring
• DNA (deoxyribonucleic acid)


  The chemical that is the stuff of heredity
• Chromosomes


  Coils of DNA that consist of smaller segments called genes, the functional units of heredity
• Every cell in the normal human body except the sex cells (sperm and ova) has 23 pairs of chromosomes—46 in all
• Zygote


  Has 46 chromosomes, 23 from the father and 23 from the mother
• Sex chromosomes


  Either X chromosomes or Y chromosomes, which govern the baby's sex
• Alleles


  Genes that can produce alternative expressions of a characteristic
• Homozygous


  When both alleles are the same
• Heterozygous


  When the alleles are different
• Dominant inheritance


  A pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed
• Recessive inheritance


  A pattern of inheritance in which a child receives identical alleles, resulting in expression of a nondominant trait
• Chromosomal abnormalities


  • Typically occur because of errors in cell division, resulting in an extra or missing chromosome
  • Down syndrome is the most common chromosomal abnormality, characterized by an extra 21st chromosome
• Sex chromosome abnormalities


  • XYY
  • XXX (Triple X)
  • XXY (Klinefelter)
  • XO (Turner)
  • Fragile X
• Cephalocaudal principle


  Development proceeds from the head to the lower part of the trunk
• Proximodistal principle


  Development proceeds from parts near the center of the body to outer ones
• Germinal stage


  1. Fertilization to 2 weeks

  2. Zygote divides, becomes more complex, and is implanted in the uterine wall
• Embryonic stage


  1. 2 to 8 weeks

  2. Organs and major systems develop rapidly (organogenesis)

  3. Critical period when embryo is most vulnerable to prenatal environmental influences
• Fetal stage


  1. 8 weeks to birth

  2. Fetus grows rapidly and organs/systems become more complex

  3. Fetuses can hear and feel
• Teratogen


  An environmental agent, such as a virus, drug, or radiation, that can interfere with normal prenatal development
• Maternal nutrition and weight

  • Women of normal weight and build who gain 16-40 lbs are less likely to have birth complications or bear babies with dangerously low or high birth weight
  • Omega-3 fatty acids and folic acid are critical in a pregnant woman's diet
• Maternal malnutrition


  • Can result in fetal growth restriction and low birth weight
  • Associated with increased risks for disease in adulthood
• Maternal physical activity and work

  • Regular exercise can prevent complications but strenuous conditions, fatigue, and long hours may increase risk of premature birth
• Drug intake during pregnancy


  Drugs may cross the placenta and are most vulnerable in early pregnancy when development is rapid
• Fetal malnutrition has been associated with increased risks for disease in adulthood
• Babies born to mothers who do not consume sufficient calories have a higher risk of death, and surviving babies may be stunted
• Regular exercise during pregnancy

  • Prevents constipation and reduces back pain
  • May reduce the risk of complications such as gestational diabetes, preeclampsia, or caesarean delivery
• Strenuous working conditions, occupational fatigue, and long working hours may be associated with a greater risk of premature birth
• Everything an expectant mother takes in makes its way to the uterus
• Drugs may cross the placenta, just as oxygen, carbon dioxide, and water do
• Vulnerability is greatest in the first few months of gestation, when development is most rapid
• Thalidomide


  A tranquilizer that was banned after it was found to have caused stunted or missing limbs, severe facial deformities, and defective organs in some 12,000 babies
• Opioids


  Babies born to drug-addicted mothers are often addicted themselves and go through withdrawal once they are born and no longer receiving the drug. Long term effects include deficiencies in growth as well as attentional memory, and perceptual problems
• Fetal alcohol syndrome (FAS)


  Characterized by a combination of retarded growth, face and body malformations, and disorders of the central nervous system
• Maternal smoking during pregnancy has been identified as the single most important factor in low birth weight
• Tobacco use during pregnancy also brings increased risks of miscarriage; growth retardation; stillbirth; small head circumference; and sudden infant death
• Marijuana exposure during pregnancy is not associated with birth defects, and it does not appear to be consistently associated with any particular pattern of cognitive or behavioral outcomes in early infancy, although some infants may show minor signs of irritability or altered sleeping patterns